From Longman Dictionary of Contemporary Englishcannoncan‧non1 /ˈkænən/ noun [countable] 
PMWa large heavy powerful gun that was used in the past to fire heavy metal balls
PMWa large heavy powerful gun that was used in the past to fire heavy metal ballsExamples from the Corpus
cannon• But it's different, there's a strange hush in the air and the endless rumbling of 50,000 cannon shells.• If all three aspects are not addressed the 240 additional cannon fodder will not remain in the system either.• That would be in the garage, right next to his cannon.• With eyes half closed he could see it as a miniature cannon.• The fog flickered around him, streaking like lightning low to the ground, or mute cannon fire.• There, they were surrounded by sand bags and soaked with a water cannon, which disabled the devices.• Only if none of these targets is available will I open fire on the big battalions with cannon.cannoncannon2 verb [intransitive always + adverb/preposition] HIT/BUMP INTOto hit someone or something while moving fastcannon into She came hurtling round the corner and cannoned straight into me.cannon off The ball cannoned off the far post.→ See Verb tableExamples from the Corpus
cannon• Koeman was involved everywhere and cracked in a 35-yard shot which cannoned back off the post after 48 minutes.• He went running off after the boy down the tunnel, dodging people and cannoning into others.• Soon he was cannoning off lime trees and, as they passed the second gates, crashed into the left-hand gatepost.• Lights blazing, their car cannoned off the kerb, tyres squealing in protest, then they were roaring along the alley.• White burst clear, but his shot cannoned off the legs of the experienced Barcelona keeper Zubizaretta.Origin cannon (1300-1400) French canon, from Italian cannone “large tube, cannon”, from canna; → CANNELLONI 